Field of the Invention
The present invention relates to a corrugated tube made of resin including bellows-like grooved portions and bellows-like ridged portions, and to a wireharness including the corrugated tube.
Description of Related Art
A wireharness used for electrical connection is routed in a vehicle such as an automobile. A wireharness which is a bundle of thin electric wires is widely known. In recent years, a wireharness for an electric vehicle or a hybrid electric vehicle, which is formed of thick high-voltage electric wires, has also been known. The wireharness may include an electric-wire protective corrugated tube. The corrugated tube is formed to include bellows-like grooved portions and bellows-like ridged portions such that the bellows-like grooved portions and the bellows-like ridged portions continuously alternate in a tube-axial direction.
A corrugated tube disclosed in JP-A-2011-254614 has a structure in which the corrugated tube is not damaged when a relatively hard electric wire cover strikes an inner surface of the corrugated tube due to transmission of vibration to a wireharness during travelling of a vehicle. The corrugated tube includes two layers, that is, an inner layer and an outer layer. According to the corrugated tube, even if the electric wire cover has hardness higher than that of the corrugated tube, an inner-layer corrugated tube, which is interposed between an outer-layer corrugated tube and the electric wire cover, serves as a cushioning member. As a result, damage to the outer-layer corrugated tube can be prevented.
It is required to provide a corrugated tube which is useful even when an electric wire cover has hardness softer than that of the corrugated tube. In other words, it is required to provide a corrugated tube with a structure in which an electric wire cover is not damaged, and degradation in a quality of the electric wire cover caused by friction or contact between the corrugated tube and the electric wire cover does not occur even when an electric wire vibrates while striking an inner surface of the corrugated tube.
Corrugated tubes with the structures illustrated in FIGS. 4 and 5 were examined, as related technology products. The corrugated tubes with the structures illustrated in FIGS. 4 and 5 do not correspond to prior art of the present invention.
In FIG. 4, a corrugated tube 1 includes outer grooved portions 2 and outer ridged portions 3. The multiple outer grooved portions 2 and multiple outer ridged portions 3 are formed in such a way as to continuously alternate in a tube-axial direction. Inner ridged portions 4 and inner grooved portions 5 are formed in an inner surface of the corrugated tube 1 so as to respectively conform to shapes of the outer grooved portions 2 and the outer ridged portions 3. A cushioning member 8 is disposed and formed on the inner surface of the corrugated tube 1 such that the cushioning member 8 is interposed between a covering outer surface 7 of an electric wire (conductive path) 6 and the inner surface of the corrugated tube 1. The cushioning member 8 is made of a material which is relatively soft and has low frictional resistance. The cushioning member 8 is formed in such a way as to cover the inner ridged portions 4 and the inner grooved portions 5, and to completely cover the inner grooved portions 5.
Since the corrugated tube 1 has a structure in which the soft cushioning member 8 having low frictional resistance is interposed between the covering outer surface 7 of the electric wire 6 and the corrugated tube 1, even if the electric wire 6 vibrates, it is possible to prevent damage to the covering outer surface 7. Degradation in the quality of the covering outer surface 7 caused by friction or contact therebetween can also be prevented.
In contrast, since the corrugated tube 1 has the structure in which the inner grooved portions 5 are completely covered with the cushioning member 8, even if the corrugated tube 1 is to be bent, the cushioning member 8 is not bent unless being extended or contracted. As a result, the corrugated tube 1 in FIG. 4 has a problem in that the tube's own flexibility is reduced.
In FIG. 5, a corrugated tube 11 includes outer grooved portions 12 and outer ridged portions 13. The multiple outer grooved portions 12 and the multiple outer ridged portions 13 are formed in such a way as to continuously alternate in a tube-axial direction. Inner ridged portions 14 and inner grooved portions 15 are formed in an inner surface of the corrugated tube 11 so as to respectively conform to the shapes of the outer grooved portion 12 and the outer ridged portion 13. A tube 18 is disposed and formed on the inner surface of the corrugated tube 11 such that the tube 18 is interposed between a covering outer surface 17 of an electric wire (conductive path) 16 and the inner surface of the corrugated tube 11. The tube 18 is fixedly attached to, and is formed integrally with the inner ridged portions 14 in such a way that the tube 18 does not strike the inner ridged portions 14. The tube 18 is relatively flexible, and is formed such that an inner tube surface is smooth.
Since the corrugated tube 11 has a structure in which the flexible tube 18 having a smooth inner surface is interposed between the covering outer surface 17 of the electric wire 16 and the corrugated tube 11, even if the electric wire 16 vibrates, it is possible to prevent damage to the covering outer surface 17. Degradation in the quality of the covering outer surface 17 caused by friction or contact therebetween can also be prevented.
In contrast, since the corrugated tube 11 has the structure in which the tube 18 is fixedly attached to the inner ridged portions 14, even if the corrugated tube 11 is to be bent, the tube 18 is stiff and is not bent. As a result, in the corrugated tube 11 in FIG. 5, the tube's own flexibility is reduced.